It is well known in the art that chlorinated solvents are useful as cleaning agents for solid substrates such as photographic film, electronic and mechanical parts, molds for casting plastics, surfaces being prepared for painting, fabrics, and various other surfaces in need of degreasing. It is also well known to persons skilled in the requisite art that chlorinated solvents are useful for dissolving materials such as polymers, waxes, oils, paints, the active ingredients in pesticides, insecticides, and fungicides, and for removing these substances from, or delivering these substances to a surface. Frequently, these substances were put into solution with a chlorinated solvent and an aerosol propellant (e.g. butane, propane, nitrogen, fluorocarbons, and carbon dioxide). The resulting solution was then suitable for various aerosol applications including cleaning and coating a substrate with the active ingredient.
One of the most common solvents used to date for such purposes is the compound 1,1,1-trichloroethane. 1,1,1-Trichloroethane has a relatively low boiling point, is non-flammable, and has a high solvency power. However, 1,1,1-trichloroethane and certain other chlorinated hydrocarbons have been theoretically linked to the depletion of the earth's protective ozone layer, and subsequently banned from commercial use in the United States. It is therefore desirable to produce a solvent, capable of multiple applications which has a relatively low boiling point, a high solvency power, is non-flammable, and most importantly, environmentally safe in that it does not deplete the ozone.
Some prior art solutions to this problem have involved using azeotropes and quasi-azeotropes based upon halohydrocarbons containing fluorine for some solvent applications where 1,1,1-trichloroethane had been formerly used. However, there are certain distinct disadvantages to using such azeotropes and quasi-azeotropes.
An azeotrope is a solution of two or more liquids, the composition of which does not change upon distillation. According to Anton, et al., (U.S. Pat. No. 5,221,361), "it is not possible to predict the formation of azeotropes and this obviously complicates the search for new azeotropic systems." Yet Anton mentions that "there is a constant effort in the art to discover new azeotropes, or azeotrope-like systems which have desirable solvency characteristics and particularly a greater range of solvency power." Such azeotropes and quasi-azeotropes are difficult and expensive to discover and produce. Furthermore, a fixed boiling point and solvency power may limit the usefulness of an azeotrope or quasi-azeotrope.
A need exists, therefore, for affordable, versatile, non-ozone depleting alternatives to traditional chlorinated solvents or to expensive azeotropic or quasi-azeotropic compositions designed to replace these chlorinated solvents.
A list of prior patents which may be of interest is provided below:
______________________________________ Patent No. Inventor Issue Date ______________________________________ 5,250,208 Merchant, et al. 5 OCT 1993 4,086,179 Schneider 25 APR 1978 3,882,568 Hill 13 MAY 1975 3,737,941 Miller, et al. 12 JUN 1973 3,635,762 Ott, et al. 18 JAN 1972 3,615,814 Ott, et al. 25 NOV 1969 ______________________________________
Hill discloses a method for cleaning acetate-based photographic film using a lint-free material that has been moistened with a cleaning solvent such as methyl chloroform. Hill does not mention the use of trans-dichloroethylene as the cleaning solvent.
Schneider teaches the use of cleaning solvents containing non-azeotropic mixture including 1,1,1-trichloroethane.
Merchant, et al. is directed to ternary azeotropic compositions which possibly include trans-dichloroethylene.